Challenger Deep is a depression in the southern Mariana Trench, near Guam, which is the deepest known place on Earth. It drops to nearly 36,000 feet below the surface of the ocean.
- About Challenger Deep -
Challenger Deep lies in the Mariana Trench, itself the deepest part of the ocean and a long depression stretching around the island of Guam. Another valley on the floor of the trench, the more recently discovered HMRG Deep, is believed to be the second-deepest place in Earth's oceans, second to Challenger Deep. The maximum depth of Challenger Deep is still unclear, but is probably around 36,000 feet. At such depths the pressure is over one thousand times what is at sea level.
Trenches and depths like this one are the result of plate tectonics, which differ on the surface of the sea to the usual processes observed on land. Under the ocean, deep trenches can be gouged out as a continental plate passes over a neighbouring oceanic plate.
There is life at the bottom of Challenger Deep, but not much of it. The Trieste reported ooze made up of diatoms as well as flatfish, although the latter may have been mistaken reports of sea cucumbers. Kaiko and Nereus spotted worms, sea cucumber, and even a shrimp, while their sample gear collected simple soft-shelled organisms. Only simple and hardy organisms can survive the immense pressure at such depths.
- Seen from the Surface -
Challenger Deep draws its name from the HMS Challenger, the ship which first located the formation through sounding in 1875 and estimated it to be about 26,800 feet deep. Challenger herself was a Royal Navy corvette formerly deployed to Australia. The so-called Challenger expedition was a multi-year oceanographic research project during the 1870s, which saw the ship disarmed and gutted to make room for laboratory and cabin space, and then sent on a sampling, depth sounding, and dredging expedition with over 240 personnel onboard. Some of those who were on the trip, like Sir John Murray, subsequently suggested that Challenger Deep was likely several thousand feet deeper than the sounding had been able to confirm.
These suspicions, however, were not followed up until the 1950s, when another Royal Navy ship named HMS Challenger, this one a purpose-built survey ship originally constructed in the 1930s. This second Challenger recorded a much greater depth, of 35,761 feet. Subsequent soundings by Japan and the U.S. National Geographic Society pushed even deeper, with the National Geographic survey of 2005 finding a point 36,021 feet below the surface of the Pacific.
- Submersible Descents -
Manned submersibles can descend to such depths, and withstand such immense pressures, only if they have been properly constructed for the trip. Nevertheless, there have been several expedition to make manned descents into Challenger Deep. The first of these was made in the Swiss-Italian bathyscaphe Trieste in 1960, by a pair of U.S. Navy-chosen operators who spent five hours on the descent phase and less than half an hour on the sea floor itself. The Trieste's dive was very nearly cut fatally short by a crack in the window of the bathyscaphe, which was one of the reasons that their time on the sea-floor itself was cut short.
Since the Trieste experiment, only unmanned submersibles have been used to plumb such immense depths. In 1995, the Japanese robotic submersible Kaiko nearly reached the bottom of the Deep, at about 35,800 feet, and collected sediment to search for marine life. More recently, in 2009, the U.S. explored Challenger Deep with the remote-controlled Nereus submersible, used by the Woods Hole institute. Nereus also collected samples for analysis at the surface.
The X Prize Foundation has committed one of its various $10 million prizes to the first private manned craft which reaches the bottom of Challenger Deep.